java.lang.VerifyError: com/zebra/sdk/settings/internal/JsonHelper

We developed an Android app a couple of years ago which prints to a ZQ520 printer using the Link-OS SDK.  Suddenly on one of our development devices, I am getting an error whenever I call the method ZebraPrinterFactory.createLinkOsPrinter().  Exception is:

java.lang.VerifyError: com/zebra/sdk/settings/internal/JsonHelper

Looking at the logcat, the underlying error seems to be:

unable to find class referenced in signature (Lcom/fasterxml/jackson/databind/ObjectMapper;)

I can fix it by adding the following to the gradle file:

compile 'com.fasterxml.jackson.core:jackson-core:2.9.4'

compile 'com.fasterxml.jackson.core:jackson-annotations:2.9.4'

compile 'com.fasterxml.jackson.core:jackson-databind:2.9.4'

but I'm not sure why it has suddenly happened.  Does anyone have any idea what is going on?

Stephen